Rotary armature miniature relay



1956 J. A. GARRATT ROTARY ARMATURE MINIATURE RELAY Filed Feb. 2, 1965 INVENTOR JOSEPH A. GARRATT BYIZW ,%/0WM ATTORNEYS fl United States Patent 3,283,272 RUTARY ARMATURE MINIATURE RELAY Joseph A. Garratt, Simsbury, Conn, assignor to Hi-G. Incorporated, Windsor Locks, Conn., a corporation of Connecticut Filed Feb. 2, 1965, Ser. No. 429,828 (Claims. (Cl. 335124) This invention relates to a relay structure and more particularly to an improved miniature relay of simplified construction and adapted for ready attachment to conventional printed circuit boards or other relay mounting devices.

Present day miniature relay structures are inherently beset with such problems as arc-overs between current conducting parts of the relay structure, a failure to provide positive operation of the contact carrying members, a necessarily high reluctance flux path, misalignment of the moving members and associated support structure during assembly and/or as a result of extended operation and relatively expensive assembly techniques associatedwith reduction in physical size of the components in achieving miniaturization without a corresponding decrease in the number of parts making up the relay assembly. In addition, the miniature relays are used in connection with electronic equipment associated with conventional aircraft or rocket structures involving extremely high inertial forces affecting the positive action of the relay. This last problem in some cases is amplified by use of moving relay components characterized by both static and dynamic imbalance.

It is, therefore, a prime object of the present invention to provide a new and improved, dynamically balanced miniature relay which is simplified in construction and which may be economically and easily manufactured, has maximum reliability and which may be advantageously hermetically sealed due to the high reliability.

It is a further object of this invention to provide an improved, low cost, miniature relay which is positive in operation regardless of inertial forces to which the relay may be subjected.

It is a further object of this invention to provide an improved miniature relay having a minimum reluctance flux path employing identical pole pieces of simplified construction and configuration.

It is a further object of this invention to provide an improved relay structure of this type in which the relay structure is connected to the header by a one-piece frame member to provide maximum rigidity to the relay.

It is a further object of this invention to provide a simplified miniature relay which allows maximum free access for lead coil terminations and contact system adjustment.

It is a further object of this invention to provide a miniature relay employing an improved armature mounting allowing close control over the end play of the pivotable armature while providing increased pivot reliability at low cost.

It is a further object of this invention to provide an improved, simplified miniature relay which provides a substantial increase in the space available for the contact system, thus allowing either heavier contacts for greater current carrying capacity or increased clearances between the metal structures and the contact system.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction 3,283,272 Patented Nov. 1, lfitifi hereafter set forth and the scope of the application which will be indicated in the appended claims.

In the drawings:

FIGURE 1 is a perspective view of a preferred embodiment of the miniature relay of the present invention;

FIGURE 2 is an exploded, perspective view of the duplicate, unitary magnetic core and pole pieces and the single element frame;

FIGURE 3 is a top plan view, partially in section, of the relay shown in FIGURE 1 taken along lines 33, showing the method of mounting the armature for dynamically balanced, limited rotation;

FIGURE 4 is a side elevation view, partially in cross section, of the armature assembly;

FIGURE 5 is a bottom plan view of the assembly of FIGURE 4;

FIGURE 6 is a top plan view of the header showing contact arrangement;

FIGURE 7 is a partial cross section view of an alternative embodiment of the improved armature mounting.

In general, the miniature relay consists of a coil and bobbin assembly having an axially extending central opening which receives a pair of oppositely oriented, identically formed magnetic sheet metal elements. Each element includes a pole piece which extends vertically adjacent the ends of the coil and bobbin and a core section at right angles to the pole pieces with the core sections received in face abutting contact within the coil opening to provide maximum flux transfer area therebetween. Pole piece extensions are directed diagonally inward, below the coil and spaced apart to form a relatively large air gap. A simple rectangular strip armature is pivotably mounted between the diagonal pole piece extensions with the strip having a longitudinal dimension greater than the air gap whereby, upon energization of the coil the ends of the armature contact respective pole piece extensions over a relatively large surface area to complete a minimum reluctance flux path. The flux path elements are fixedly positioned on the relay header by a single element frame member which may be formed of thin sheet metal by progressive die techniques. The frame member and a lower armature support welded to the bottom ends of the pole pieces provide a rigid and highly accurate mount for the pivotable armature. The lower armature support acts in conjunction with the armature itself to hold a leaf spring in operative position to bias the armature in open gap position to maintain positive relay operation regardless of excessive inertial forces to which the relay may be subjected. This simplified relay arrangement allows increased spaced between relay contacts, lessens the danger of arcing between current carrying contacts and the relay frame even under increased load as a result of enhanced contact spacing.

Referring to the drawings, the miniature relay 10 comprises several principal assemblies or elements including the coil and bobbin assembly 12, the unitary core and pole piece assembly 14, the single element bridge or frame member 16, the armature assembly 18 and the header 20.

The simplified relay structure 10 is constructed of a relatively few but necessary parts providing maximum spacing between the elements, positive relay operation and ensured reliability with the miniature relay being maintenance free and adaptable for hermetically sealing. This may be achieved by suitably attaching as by soldering or welding a cover or can (not shown) to the base or header 20. The header 20 may be formed wholly of insulative material or may be formed from east or stamped metal, in this case it will include a series of spaced apertures 22 through which project the current carrying terminal members 24. In the relay structure shown, the configuration of the header is generally rectangular with the header acting as a supporting base for the components. It includes one or more recesses 26 formed therein which receive depending tabs 28 formed integrally with the bridge or fraine member 16. The terminal pins 24 are positioned within the openings 22 of the header and secured to the header by glass insulator beads 30. The pins may include a generally flattened portion intermediate the ends (not shown) which is positioned within the glass insulator area to prevent both axial and rotational movement of the pins with respect to header 20. One or more of the glass beads 30, used to position the terminal pins 24 with respect to the header, may be colored while the remaining glass beads may be clear, thus allowing the colored bead to be used as a polarizing means to ensure proper placement of the miniature relay on the printed circuit 'board.

Mounting of the magnetic relay components to the base header 20 is accomplished by the use of a single element, box-style frame or bridge member 16 formed into five planes to provide maximum rigidity. The design, which is most apparent in FIGURE 2, allows the unit to be produced on progressive type dies at minimum cost. As mentioned previously, depending tabs 28 are received within appropriate recesses 26 for securing the frame member to the base or header. The frame 16 is therefore provided with a pair of upstanding, spaced side walls 32, joined by a horizontal, diagonal support section 34, the side portions 32 terminating in right angled ends 36. In like manner to most of the elements forming the new and improved relay structure, the configuration of one half of the frame member 16 is identical to the other half. The bridge member may be formed of a nickel-silver alloy and in progressively molding the single element bridge to the configuration shown, the diagonally formed horizontal support section 34 is progressively embossed and punched to form a circular boss 38 and an armature support receiving hole 40, the embossed section 38 thus provides a circular recess within the upper surface of the horizontal segment 34 and a corresponding downwardly projecting surface adjacent the opening 40, FIGURE 7.

The magnetic core and pole piece assembly 14, is supported by a frame member 16 and is rigidly coupled there to. As best seen in FIGURE 2, the magnetic core and pole piece assembly consists of a pair of duplicate, unitary magnetic core and pole pieces 44 which include a longitudinally formed rectangular central section 46 at right angles to the pole piece sections 48, the pole pieces terminating at the lower end in inwardly directed, diagonally oriented, armature contacting extensions. The integral magnetic core and pole piece sections may be stamped out of iron stock of low reluctance to provide the entire electromagnetic flux path with the exception of the pivotable armature. This configuration provides for minimum cost and fabrication, since again it may be produced on progressive dies, while providing optimum magnetic characteristics due to the broad contact area provided by longitudinal sections 46 for flux transfer between the two mating parts within the coil and bobbin assembly 12. Since the only magnetic gap, other than the air gap existing between the armature and the pole piece extensions 50, is that across the relatively large contact area between the mating core sections 46, the magnetic flux carrying efiiciency is greatly enhanced.

The pole piece sections 48 are received within an opening 52 formed between the diagonal, horizontal section 34 of the frame member and the right angled end sections 36. The inner face of the end section 36 is coupled to the outer surface of the pole piece by spot welding the two elements together at a single point indicated at 54 in FIGURE 1. By spot welding the end faces of the pole pieces to the relay frame, extreme rigidity is provided in mounting the magnetic structure to the relay while providing maximum immunity to vibration and shock.

As mentioned previously, the duplicate, magnetic core and pole pieces 44 act to hold the bobbin and coil assembly 12. In this respect, the bobbin 56 is of conventional configuration and includes a pair of spaced ends 58-59, coupled by a rectangular core (not shown) and includes a rectangular central opening 60 which acts to receive the core sections 46. The sections 46 are inserted from either end when assembling the bobbin to the core and pole piece assembly. The bobbin may of course be formed of insulative material and acts to hold a wound wire coil 62 concentrically thereabout. As indicated in FIGURE 1, a coil lead 64 extends from the coil 62 to one of the terminal members 24 and is soldered or welded thereto at 68 in the conventional manner. A return lead (not shown) is positioned on the opposite side of the relay. Thus, current is delivered through lead 64 to excite the windings 62 and operate the relay. In this manner, the bobbin assembly 12 is carried by the magnetic core and pole piece assembly 14 which is rigidly coupled to frame 16.

The remaining element of the fiux path is the armature 75} forming a part of the armature assembly 18. The armature 70 may also be formed of the same iron material forming the unitary magnetic core and pole piece segments 44 and is a simple rectangular strip member. The mounting of armature 70 is a specific improvement in the present invention to reduce magnetic force operating requirements while insuring reliable armature movement. As most clearly seen in FIGURE 4, the armature is provided with a pair of parti-spherical depressions 72 and 72A positioned at the armature midameter of the polished steel ball 74 and 74A. An annular washer 73 of Teflon or other high surface lubricity material is provided lbetween the armature and support 76 and a similar washer 75 is provided between armature and frame member section 34. The armature is assembled with a ball in each depression, which balls are trapped in the apertures 40 and 40A thereby to pnovide ball-bearing armature mounting in an inexpensive manner not subject to minor alignment problems.

As an alternative armature mounting, the arrangement of FIGURE 7 is provided wherein the balls 74B (only one of which is illustrated) are spot welded to armature and are received in aperture 40B formed in boss 38B, which apertures are slightly larger than the outside diameter of the ball. With such an arrangement, the annular washer 73B, also formed of a high lubricity material, functions as a thrust bearing.

The lower armature support member 76 is formed of strap configuration, being welded to the bottom surface of pole piece ends 48 at 78, thereby fixing the position of the lower armature support member 76 with respect to the remaining elements of the relay structure, and may be formed of non-magnetic material. The lower armature support member 76 includes an upstanding tab section 84. The inner end 88 of the spring member is bent diagonally to the main body. The flattened diagonal section 88 is preferably spot welded to one armature face 89 with the free end 90 acting upon the bent-up tab 84 of the lower armature support member 76. In the position shown in the drawing, a small spring force is exerted by the free end 90 on the armature assembly 18 tending to pivot the armature clockwise as seen in FIG URE 3 from above, holding the ends of the armature 70 away from the pole piece extensions 50 and thus providing the maximum air gap 92 therebetween. The leaf spring 86 forms a simplified biasing means and at the same time ensures positive action of the relay. The lower support member 76 includes a second upstanding tab or lug 85, positioned on the opposite side of the support member from tab 84 and limits the rotation of the armature assembly 18 under the bias of the armature leaf spring 86. The design further provides an extremely inexpensive method of providing armature restoring force with the damping action virtually eliminating all sharp resonances in the armature mounting system.

With the simplified miniature relay construction described in detail above, it is apparent that great space efficiency is provided within even the relatively extermely small relay construction shown. With the substantial increase in space available for the contact system between the motor and the header assembly, contact size and/or current carrying ability may be increased without compromising the danger of possible arc-over between the contact system and the frame of the relay.

With regard to the contact system, the stationary and movable contacts and their specific orientation may be seen most advantageously when viewing FIGURE 6. In the relay structure of the embodiment shown, limited rotation of the armature about a vertical axis acts to selectively move a pair of c'ontact members 100 and 102 carrying contact faces 104, respectively from one fixed contact member 106 to the other fixed contact member 108. The fixed and movable contact members are electrically coupled to respective terminals 24 extending through header 20. The movable contact members 106 and 102 are in the form of cantilever spring members in which the inner ends are rigidly attached to terminals 24- and in which the outer ends are normally biased in the manner shown such that the contact faces 104 are electrically coupled to fixed contacts 106. The terminal ends of the fixed and movable contact members may be preferably welded to their respective terminal pins 24. The two terminal pins 24 not shown connected to fixed or movable contact members are, of course, coupled to the electrical leads emanating from the electromagnetic coil 62, and thus provide selective energization for the coil.

The flexible contact members 1130 and 102 may be formed of a conductive metal alloy, such as nickel-clad molybdenum while the contact buttons 104 afiixed to the free ends thereof may be formed of highly conduc- Itive silver-clad nickel alloy. With the movable contact members 100 and 102 biased in the position shown, actuator means must be coupled to the armature for physically moving the movable contacts from the position shown to a position in which they make contact with fixed contacts 168. In this respect, the armature assembly 18 carries a pair of formed wire actuators 110 or pushers which are welded at 112 to opposite sides of the armature 70 and depend downwardly therefrom, terminating with the ends covered by insulative glass contact balls 114. As indicated in FIGURE 6, the balls 114 are positioned in the dotted line position shown with the magnet coil de-energized and as a result of energization of the coil, the armature assembly 18 pivots to move the balls 114 into contact with the sides of the movable contact members 1490 and 102 respectively, to cause the contact button portions 104 to move from fixed contacts 106 to fixed contacts 108. The movement of the balls is shown by arrows 116 in FIGURE 6.

In assembling the miniature relay, the bobbin assembly 12 is positioned on the core and pole piece assembly by inserting the respective identical pieces 44 in opposite sides of the coil bobbin aperture 6@ and sub sequently spot welding the pole piece sections 48 to the ends 36 of the frame member 16. The armature assembly may then be inserted between the fiat diagonal section 34 of the frame member 16 and the lower armature support member 76 with the lower armature sup port member '76 spot welded at points 73 to the bottom of the pole piece sections 48. This assembly may then be coupled to the header 24 which already carries the contact structure by suitably coupling the frame 16 to the header 21 at the frame tab portions 28 and the appropriate recesses 26 Within the header.

From the above description, it is readily apparent that the magnetic flux carrying elements as well as the metallic supporting elements for the relay component are all formed of thin metal stock, readily bent in progressive die fashion to form an extremely simplified but effective miniature relay structure greatly reducing the number of individual elements over known miniature relay configuration to form a low reluctance magnetic path. For instance, when the armature 70 moves into a contact position with respect to pole piece extensions 50, a large surface area of contact exists between the pole piece extensions and the armature with minimum reluctance. Further, the armature itself comprises a simple rectangular strip having no specially formed faces to ensure effective and positive relay operation, in response to energization of the coil and bobbin assembly of the coil 62. It is further obvious that to effect a mechanically rigid structure, welding is employed in only two places, identified at 54 where the main pole piece section 48 is fixedly coupled to the end portion of the frame 16 and at 78 where the lower armature support member 76 is fixedly coupled to the bottom surfaces of the same simplified core and pole face element 44. Of course, the frame can also be afiixed by welding to the header 20. Since the armature itself is a simple rectangular strip and is pivoted centrally and since it carries switch actuators of identical configuration positioned an equal distance from the center of rotation, the armature is both statically and dynamically balanced. Positive operation is therefore ensured regardless of inertial forces to which the relay structure may be subjected.

As will be apparent to persons skilled in the art, various modifications and adaptations of the structure above described will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.

I claim:

1. A low reluctance magnetic path for a simplified miniature relay having a coil with an axially extending opening formed therein; a core and pole piece assembly formed by a pair of oppositely oriented, identically formed magnetic sheet metal elements, each of said elements including a pole piece extending vertically adjacent the ends of the coil, a core section bent inwardly, at right angles to said pole piece, the respective core sections received in face abutting contact within said coil opening to provide maximum flux transfer area therebetween, pole piece extensions extending diagonally inward, exteriorly of said coil to form a relatively large air gap therebetween, a strip armature having a longitudinal dimension greater than said air gap and means for pivotably positioning said armature between said oppositely oriented, diagonal pole piece extensions whereby, upon energization of said coil, the ends of said armature contact respective pole piece extensions over a relatively large surface area to complete said low reluctance flux path.

2. A simplified miniature relay comprising: a thin sheet header, at least one fixed contact supported on the upper surface of said header, a movable contact positioned adjacent to said fixed contact for movement toward and away therefrom, a single element frame member including a pair of spaced end sections fixedly attached to said header and rising vertically therefrom, said frame member further including a horizontal section joining said spaced end members at the upper end thereof, a core and pole piece assembly formed by a pair of oppositely oriented, identically formed magnetic sheet metal elements, each of said elements including a pole piece extending vertically from said frame end sections and mechanically fixed thereto, a coil having an axially extending opening formed therein, a core section bent inwardly at right angles to said pole piece with respective core sections received in face abutting contact within said coil opening to provide maximum flux transfer area therebetween, an armature in the form of a thin magnetic strip, a lower armature support member coupled to the lower ends of said pole pieces and extending transversely therebetween, spaced from said horizontal section of said frame member, aligned openings formed within said lower armature support member and said horizontal frame section, means for pivotably supporting said armature within said openings for limited rotation about a vertical axis, means for biasing the ends of said armature away from said pole pieces, and means carried by said armature for moving said movable contact member with respect to said fixed contact member whereby, upon energization of said coil, the ends of said armature contact said pole pieces to complete a low reluctance flux path therebetween.

3. The apparatus as claimed in claim 2 wherein said aligned openings are formed centrally of said pole pieces within said horizontal frame section and said lower armature support, and said magnetic str-ip armature is pivotally supported by a pair of balls received within said aligned openings to allow free rotation of said armature about said vertical axis.

4. The apparatus as set forth in claim 3 wherein said balls are fixed to said armature.

5. A shock and vibration resistant mounting for supporting an armature in an electromagnetically operated relay for movement toward and away from poles of an electromagnet comprising first and second rigid support members. disposed on opposite sides of the armature, a generally concave depression on each side of the armature and a ball positioned in each depression and fixedly secured to the armature for movement therewith, each of said rigid support members including means holding each ball in position in the armature depression thereby to support said armature between said support members.

6. A simplified miniature relay construction comprising: a header formed of sheet stock, a frame member rigidly coupled to said header, said frame member including spaced end portions rising from said header, said frame member further including side portions at right angles to said end portions and an armature support section extending transversely of said side portions at the upper end thereof, a coil having an axially extending opening formed therein, a core and pole pieceassembly formed by a pair of oppositely oriented, identically formed magnetic sheet stock elements, means for rigidly coupling said pole pieces to said frame end portion, each of said elements including a core section bent inwardly at right angles to said pole piece with respective core sections received in face abutting contact within said coil opening to provide a maximum flux transfer area therebetween, a lower armature support extending longitudinally between said frame end portions, means for fixedly attaching the ends of said lower armature support member to the bottom of said pole piece with said lower armature support member spaced from said upper transverse frame section, an armature in the form of a thin rectangular strip, means for positioning said armature between said transverse frame member and said lower armature support member for limited rotation about a vertical axis, said armature having a longitudinal dimension greater than the air gap existing between said pole pieces, and means for biasing said armature in open gap position whereby, upon energization of said coil, the ends of said armature contact said pole pieces to complete a low reluctance flux path therebetween.

7. A shock and vibration resistant mounting for supporting an armature in an electro'magnetically operated relay for movement toward and away from poles of an electromagnet comprising first and second support members disposed on opposite sides of the armature, a generally concave depression on each side of the armature and a ball positioned in each said depression, each of said support members including an aperture having a diameter less than the maximum ball diameter and holdg ing each said ball in trapped position in its armature depression thereby to support the armature between said support members, and a pair of pole piece extensions extending diagonally inward between said first and second support members to form a relatively large magnetic air gap therebetween with the plane of said pole piece extensions being parallel to the plane of the armature whereby, upon energization of the electromagnet, the ends of the armature contact said pole piece extensions over a relatively large surface area to complete a low reluctance flux path therewith.

8. The mounting as set forth in claim 5 wherein said means holding each said ball in position includes a pair of oppositely disposed apertured bosses provided in said first and second support members and positioned on upper and lower surfaces of the armature, centrally thereof, and perpendicularly thereto, said apertured bosses being aligned and engageable with said balls whereby the armature pivots freely within said support members.

9. The apparatus as claimed in claim 6 wherein said lower armature support member includes an upstanding lug positioned at one side thereof in the path of said moving armature adjacent one end of said relay, and said lower armature support member further includes a second upstanding lug positioned at the same end of said relay on the opposite side of said pivotable armature, a leaf spring, means for fixing one end of said leaf spring to said armature on the side of said armature opposite said upstanding lugs, said leaf spring being of such a configuration and positioned with the free end thereof contacting said second lug whereby said spring biasing force of said leaf spring tends to pivot said armature away from said pole piece extensions.

10. A simplified miniature relay comprising a rectangular header including a series of spaced apertures formed therein, a series of terminal pins extending at right angles to the plane of said header through respective apertures, at least one fixed contact member coupled to one of said pins and positioned on the upper surface of said header, at least one movable contact member, one end of said movable contact member being coupled electrically to a second terminal pin, means for positioning said movable contact member on the upper surface of said header in operative relationship to said fixed contact member, a single element frame member including spaced ends fixedly attached to said header and rising vertically therefrom, said frame member further including spaced side portions extending at right angles to said ends and a transverse armature support section extending between said side portions across the top thereof, said frame armature support section being spaced from said frame end sections, to form respective gaps therebetween, a coil having an axially extending opening formed therein, a core and pole piece assembly formed by a pair of oppositely oriented, identically formed magnetic sheet stock elements, each of said elements including a pole piece, said pole piece extending vertically with the lower ends of said pole pieces being received within said gap between said frame formed between said transverse frame section and the ends thereof, means for rigidly connecting said pole pieces to said frame ends, respective core sections bent inwardly at right angles to said pole pieces with the core sections being received in face abutting contact within said coil opening to provide maximum flux transfer area therebetween and acting to support said coil, pole piece extensions extended diagonally inward, said pole piece extensions being positioned exteriorly of said coil beneath said transverse frame section and forming therebetween a relatively large air gap, a lower armature support member, means for rigidly coupling said armature support member to the bottom of the respective pole pieces with said lower armature support member being spaced from said upper transverse armature frame section, an armature in the form of a thin strip of magnetic material having a longitudinal dimension greater than said air gap, means for coupling said armature to said lower armature support member and said frame member transverse section for pivotable movement about a vertical axis, means carried by said armature in operative relationship to said movable contact member for opening and closing said relay contacts, means biasing said armature in open gap position whereby, upon energization of said coil, the ends of said armature rotate in opposition to said biasing means to a position where the ends of said armature contact the faces of said diagonal pole piece extensions over a relatively large surface area to complete said low reluctance flux path.

References Cited by the Examiner BERNARD A. GILHEANY, Primary Examiner. B. DOBECK, JOSEPH BAKER, Assistant Examiners, 

1. A LOW RELUCTANCE MAGNETIC PATH FOR A SIMPLIFIED MANIATURE RELAY HAVING A COIL WITH AN AXIALLY EXTENDING OPENING FORMED THEREIN; A CORE AND POLE PIECE ASSEMBLY FORMED BY A PAIR OF OPPOSITELY ORIENTED, IDENTICALLY FORMED MAGNETIC SHEET METAL ELEMENTS, EACH OF SAID ELEMENTS INCLUDING A POLE PIECE EXTENDING VERTICALLY ADJACENT THE ENDS OF THE COIL, A CORE SECTION BENT INWARDLY, AT RIGHT ANGLES TO SAID POLE PIECE, THE RESPECTIVE CORE SECTIONS RECEIVED IN FACE ABUTTING CONTACT WITHIN SAID COIL OPENING TO PROVIDE MAXIMUM FLUX TRANSFER AREA THEREBETWEEN, POLE PIECE EXTENSION EXTENDING DIAGONALLY INWARD, EXTERIORLY OF SAID COIL TO FORM A RELATIVELY LARGE AIR GAP THEREBETWEEN, A STRIP ARMATURE HAVING A LONGITUDINAL DIMENSION GREATER THAN SAID AIR GAP AND MEANS FOR PIVOTABLY POSITIONING SAID ARMATURE BETWEEN SAID OPPOSITELY ORIENTED, DIAGONAL POLE PIECE EXTENSIONS WHEREBY, UPON ENERGIZATION OF SAID COIL, THE ENDS OF SAID ARMATURE CONTACT RESPECTIVE POLE PIECE EXTENSIONS OVER A RELATIVELY LARGE SURFACE AREA TO COMPLETE SAID LOW RELUCTANCE FLUX PATH. 